1. Field of the Invention
This invention relates to secure systems in which access to confidential data is restricted, including, but not limited to, pay-television.
2. Description of the Related Art
In secure systems, it is usually necessary that access to data of a confidential nature is restricted. Access to data in such systems is often restricted by encrypting or otherwise scrambling the data by means of particular secret keys. Data may then be accessed by authorized users by decrypting the data using a specified key known only to those users. Although such schemes provide a high degree of security, if the keys used to encrypt or decrypt data do become known to persons not entitled to access the data, then the system would be breached.
We have appreciated that the security of secure systems is increased if keys used to encrypt and decrypt confidential data are regularly updated. We have further appreciated that a reliable and efficient mechanism for updating keys is desirable.